Computed tomography is known in the art and comprises in some cases an approach to object imaging in which a thin X-ray beam (such as a fan beam) rotates around an object. Many small detectors measure the amount of X-rays that make it through the object and a computer then constructs a series of cross-sectional scans across a common axis.
A problem can arise when the object being scanned is larger than the relevant dimensions of the detector (allowing for geometrical magnification) in that portions of the object will not be adequately scanned. (It should be understood that, as used herein, “detector” refers to a device capable of providing multiple signals across a line, across several adjacent lines, or across an area as the case may be.) Offset rebinning represents a prior art approach to dealing with this problem. By this approach the detector is offset with respect to a line that intersects the X-ray source and the center of rotation about which the object and X-ray source/detector rotate with respect to one another. In general, such a placement has the detector extending to one side of this line. So configured, of course, no scanning data is obtained for the opposing side of the line. Rebinning, however, provides for capturing this missing data when the object and X-ray source/detector have later rotated 180 degrees. Simply put, offset rebinning permits at least one half of an object to be initially scanned with missing portions of the object being scanned 180 degrees later.
For at least some applications offset rebinning provides an adequate solution. Even when allowing for data feathering of the so-called forward and reverse data, the detector effectively becomes about 80% larger. That is, with offset rebinning, an object up to about 80% larger can be accommodated as compared to more typical third generation processing with the same detector. This is not to say, however, that offset rebinning has completely addressed all needs in this regard. A problem can occur, for example, when an object to be scanned is larger than that which can otherwise be accommodate by an offset rebinning approach.
In such a case, a typical thought might be to simply use a larger detector and/or to chain multiple detectors together in an abutted fashion. Unfortunately, it may be impractical and/or commercially impossible to obtain a larger detector. Similarly, satisfactory results are ordinarily not obtained by abutting two or more detectors against one another, as several types of detectors, such as but not limited to image intensifiers and flat-plate detector arrays, cannot be abutted without incurring a certain amount of dead space between their active detection areas. Such a configuration, for example, typically leaves a coverage gap of at least some size between adjacent detectors. This gap, in turn, yields scanning results that suffer from undesirable artifacts, ambiguity, and the like.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding respective areas of inquiry and study except where specific meanings have otherwise been set forth herein.